A mobile communications network is typically made up of a plurality of cells. Each cell is provided by a radio base station, with each base station connected to a mobile switching center or a packet service node that manages communications sessions between mobile stations and terminals coupled to a public switched telephone network (PSTN) or a packet-based data network. Communications between mobile stations and base stations are performed over wireless links.
A service that can be provided by a wireless communications network is a location service (for determining a position of a mobile station). There are two general categories of location services: emergency (E911) services (ES); and value added services (VAS) or commercial services, such as navigational services (e.g., services to find a store or other location), locate-me type services, and so forth.
A wireless communications network that is capable of providing location services typically includes base stations, a mobile switching center (MSC), a mobile position center (MPC), and one or more position determining entities (PDEs). The MPC receives location requests from either an ES network or a VAS-related entity. The MPC selects a PDE to interact with the mobile station and the MSC in the determination of the location of the mobile station.
Standards that define protocol messaging for location services in a wireless communications network include the TIA/EIA/IS-801, TIA/EIA/IS-881, and J-STD-036-A standards. Messaging exchanged between the MPC, PDE, MSC, and mobile station for VAS-related location services is defined by TIA/EIA/IS-881, while messaging for ES-related location services is defined by J-STD-036-A. Per both standards, the MSC may receive the InterSystemPositionRequest INVOICE (ISPOSREQ) message from the serving MPC. The ISPOSREQ message may contain a field, referred to as the LCS (location services) Client Type (CTYP) field, to indicate whether or not the entity requesting location services is requesting emergency services. The absence of the CTYP field indicates that the requesting entity is ES-related.
The TIA/EIA/IS-801 standard defines protocol messaging conveyed between the mobile station and the PDE that includes positioning determination data messages (PDDMs), where each PDDM contains one or more request and/or response elements. PDDMs are conveyed over a traffic channel for both ES and VAS-related location services.
In certain scenarios, an ES-related entity, such as a public safety answering point (PSAP) within an ES network, may attempt to contact the mobile station user after an emergency services call has ended due to either a call drop (due to signal attenuation or other reason) or when the PSAP may want to call back the mobile station user to obtain more information or to obtain an updated position of a moving mobile station. Should the callback be initiated by the PSAP for the purpose of location services, the PDE, MSC, base station, and mobile station may in some scenarios treat the location request as if the location request were related to a value-added service, since these network elements typically cannot distinguish a network-initiated location request related to ES callback from a network-initiated, value-added service location request. The mobile station is also unable to determine whether a location request is VAS- or ES-related by examining the content of a PDDM. Thus, if a mobile station is configured by a user such that a mobile station disables all location services except for ES-related services, the mobile station may reject ES-related request elements received in a PDDM over a traffic channel if the mobile station incorrectly assumes that the PDDM is from a VAS-related entity. The inability to obtain the mobile station's precise position may result in safety concerns.
In some cases, an ES-related entity may wish to perform an idle-mode location query in which the ES-related entity attempts to obtain the location of a mobile station that is idle without having to establish a voice call. To do so, a page with a particular service option (such as service option 35 or 36) for location services is sent to the mobile station. However, the mobile station has no way of knowing whether or not the page is related to an ES location service. If the mobile station is configured to accept ES-related location requests only, the mobile station may incorrectly assume that the page is VAS-related and thus reject the page's service option.
In other scenarios, a mobile station configured to accept only ES-related location services may erroneously accept VAS-related location requests if the mobile station incorrectly determines that the VAS-related location request is ES-related. In either case, the inability to accurately distinguish between ES-related and VAS-related location requests results in erroneous processing of such location requests in a wireless communications network.